Collecting Tabular Input

Sometimes we want to collect user input in a batch mode. That is, the user
can enter the information for multiple model instances and submit them all
at once. We call this tabular input because the input fields are
often presented in an HTML table.

To work with tabular input, we first need to create or populate an array
of model instances, depending on whether we are inserting or updating the
data. We then retrieve the user input data from the $_POST variable and
assign it to each model. A slight difference from single model input is
that we retrieve the input data using $_POST['ModelClass'][$i] instead of
$_POST['ModelClass'].